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Strigolactones (SLs) are newly discovered plant hormones that modulate a variety of physiological and biochemical processes and plant stress responses. In this study, SLs' synthetic analog, GR24, significantly improved the growth of tomato seedlings under salt stress, while SLs' synthesis inhibitor, TIS108, inversed the positive role of SLs, indicating that SLs could effectively enhance salt-stress resistance in tomato. To further explore the mechanism of SL-modulated trehalose (Tre) in response to salt stress, Tre metabolism was analyzed during this process. GR24 increased the endogenous Tre and starch contents and decreased the glucose (Glu) level under salt-stress conditions. Additionally, the TPS and TPP activities were enhanced by GR24 and the activity of THL was inhibited by GR24 under salt stress; thereafter, Tre biosynthesis-related genes, including TPS1, TPS2, TPP1, and TPP2, were also upregulated by GR24 under salt stress. However, the function of GR24 in Tre metabolism was inhibited by TIS108. Thus, the results indicated that GR24 improved the expression levels or activities of Tre biosynthesis-related genes or enzymes and inhibited the transcript level or activity of genes or enzymes related to Tre degradation, respectively, resulting in an increase in the endogenous Tre level and, therefore, weakening the salt toxicity of tomato seedlings. [ABSTRACT FROM AUTHOR]

Melatonin (MT) and nitric oxide (NO) act as signaling molecules that can enhance cadmium (Cd) stress resistance in plants. However, little information is available about the relationship between MT and NO during seedling growth under Cd stress. We hypothesize that NO may be involved in how MT responds to Cd stress during seedling growth. The aim of this study is to evaluate the relationship and mechanism of response. The results indicate that different concentrations of Cd inhibit the growth of tomato seedlings. Exogenous MT or NO promotes seedling growth under Cd stress, with a maximal biological response at 100 μM MT or NO. The promotive effects of MT-induced seedling growth under Cd stress are suppressed by NO scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (cPTIO), suggesting that NO may be involved in MT-induced seedling growth under Cd stress. MT or NO decreases the content of hydrogen peroxide (H2O2), malonaldehyde (MDA), dehydroascorbic acid (DHA), and oxidized glutathione (GSSG); improves the content of ascorbic acid (AsA) and glutathione (GSH) and the ratios of AsA/DHA and GSH/GSSG; and enhances the activities of glutathione reductase (GR), monodehydroascorbic acid reductase (MDHAR), dehydroascorbic acid reductase (DHAR), ascorbic acid oxidase (AAO), and ascorbate peroxidase (APX) to alleviate oxidative damage. Moreover, the expression of genes associated with the ascorbate–glutathione (AsA-GSH) cycle and reactive oxygen species (ROS) are up-regulated by MT or NO under Cd conditions, including AAO, AAOH, APX1, APX6, DHAR1, DHAR2, MDHAR, and GR. However, NO scavenger cPTIO reverses the positive effects regulated by MT. The results indicate that MT-mediated NO enhances Cd tolerance by regulating AsA-GSH cycle and ROS metabolism. [ABSTRACT FROM AUTHOR]

Strigolactones (SLs), as a new phytohormone, regulate various physiological and biochemical processes, and a number of stress responses, in plants. In this study, cucumber 'Xinchun NO. 4' is used to study the roles of SLs in seed germination under salt stress. The results show that the seed germination significantly decreases with the increase in the NaCl concentrations (0, 1, 10, 50, and 100 mM), and 50 mM NaCl as a moderate stress is used for further analysis. The different concentrations of SLs synthetic analogs GR24 (1, 5, 10, and 20 μM) significantly promote cucumber seed germination under NaCl stress, with a maximal biological response at 10 μM. An inhibitor of strigolactone (SL) synthesis TIS108 suppresses the positive roles of GR24 in cucumber seed germination under salt stress, suggesting that SL can alleviate the inhibition of seed germination caused by salt stress. To explore the regulatory mechanism of SL-alleviated salt stress, some contents, activities, and genes related to the antioxidant system are measured. The malondialdehyde (MDA), H2O2, O2−, and proline contents are increased, and the levels of ascorbic acid (AsA) and glutathione (GSH) are decreased under salt stress conditions, while GR24 treatment reduces MDA, H2O2, O2−, and proline contents, and increases AsA and GSH contents during seed germination under salt stress. Meanwhile, GR24 treatment enhances the decrease in the activities of antioxidant enzymes caused by salt stress [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)], following which antioxidant-related genes SOD, POD, CAT, APX, and GRX2 are up-regulated by GR24 under salt stress. However, TIS108 reversed the positive effects of GR24 on cucumber seed germination under salt stress. Together, the results of this study revealed that GR24 regulates the expression levels of genes related to antioxidants and, therefore, regulates enzymatic activity and non-enzymatic substances and enhances antioxidant capacity, alleviating salt toxicity during seed germination in cucumber. [ABSTRACT FROM AUTHOR]

Anthocyanins act as polyphenolic pigment that is ubiquitously found in plants. Anthocyanins play a role not only in health-promoting as an antioxidant, but also in protection against all kinds of abiotic and biotic stresses. Most recent studies have found that MYB transcription factors (MYB TFs) could positively or negatively regulate anthocyanin biosynthesis. Understanding the roles of MYB TFs is essential in elucidating how MYB TFs regulate the accumulation of anthocyanin. In the review, we summarized the signaling pathways medicated by MYB TFs during anthocyanin biosynthesis including jasmonic acid (JA) signaling pathway, cytokinins (CKs) signaling pathway, temperature-induced, light signal, 26S proteasome pathway, NAC TFs, and bHLH TFs. Moreover, structural and regulator genes induced by MYB TFs, target genes bound and activated or suppressed by MYB TFs, and crosstalk between MYB TFs and other proteins, were found to be vitally important in the regulation of anthocyanin biosynthesis. In this study, we focus on the recent knowledge concerning the regulator signaling and mechanism of MYB TFs on anthocyanin biosynthesis, covering the signaling pathway, genes expression, and target genes and protein expression. [ABSTRACT FROM AUTHOR]